If the object really is Planet Nine, it would be larger than Neptune and exist 700 times further from the sun than Earth.

The presence of another planet in the solar system could explain the odd movements of some of the bodies in the Kuiper Belt.

Using two infrared space telescopes and a 23-year gap, scientists may have spotted a mysterious, slow-moving object beyond ...

A new look through decades-old data has unveiled some of the most compelling evidence yet of a hidden ninth planet in the far ...

The solar system consists of our star, the sun, and everything bound to it by gravity: the planets Mercury, Venus, Earth, ...

Astronomers have detected a promising sign of a ninth planet lurking at the the farthest reaches of the Solar System.

A team of astronomers poring through old astronomical data may have seen a candidate for the elusive Planet Nine – a ...

A powerful new observatory is the best hope yet for finding the elusive Planet 9, a large planet that some scientists say is hidden in our solar system.

Astronomers from MIT have uncovered a dramatic celestial spectacle: a Mercury-sized exoplanet that is rapidly disintegrating ...

For about a decade, he and other researchers have been trying to prove that the so-called "Planet 9" exists. So far, the only evidence has come from some oddities in the orbits of small Pluto-like ...